// Tencent is pleased to support the open source community by making RapidJSON
// available.
//
// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All
// rights reserved.
//
// Licensed under the MIT License (the "License"); you may not use this file
// except in compliance with the License. You may obtain a copy of the License
// at
//
// http://opensource.org/licenses/MIT
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.

#ifndef RAPIDJSON_FILEREADSTREAM_H_
#define RAPIDJSON_FILEREADSTREAM_H_

#include <cstdio>
#include "stream.h"

#ifdef __clang__
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(padded)
RAPIDJSON_DIAG_OFF(unreachable - code)
RAPIDJSON_DIAG_OFF(missing - noreturn)
#endif

RAPIDJSON_NAMESPACE_BEGIN

//! File byte stream for input using fread().
/*!
    \note implements Stream concept
*/
class FileReadStream {
 public:
  typedef char Ch;  //!< Character type (byte).

  //! Constructor.
  /*!
      \param fp File pointer opened for read.
      \param buffer user-supplied buffer.
      \param bufferSize size of buffer in bytes. Must >=4 bytes.
  */
  FileReadStream(std::FILE *fp, char *buffer, size_t bufferSize)
      : fp_(fp),
        buffer_(buffer),
        bufferSize_(bufferSize),
        bufferLast_(0),
        current_(buffer_),
        readCount_(0),
        count_(0),
        eof_(false) {
    RAPIDJSON_ASSERT(fp_ != 0);
    RAPIDJSON_ASSERT(bufferSize >= 4);
    Read();
  }

  Ch Peek() const { return *current_; }
  Ch Take() {
    Ch c = *current_;
    Read();
    return c;
  }
  size_t Tell() const {
    return count_ + static_cast<size_t>(current_ - buffer_);
  }

  // Not implemented
  void Put(Ch) { RAPIDJSON_ASSERT(false); }
  void Flush() { RAPIDJSON_ASSERT(false); }
  Ch *PutBegin() {
    RAPIDJSON_ASSERT(false);
    return 0;
  }
  size_t PutEnd(Ch *) {
    RAPIDJSON_ASSERT(false);
    return 0;
  }

  // For encoding detection only.
  const Ch *Peek4() const {
    return (current_ + 4 - !eof_ <= bufferLast_) ? current_ : 0;
  }

 private:
  void Read() {
    if (current_ < bufferLast_)
      ++current_;
    else if (!eof_) {
      count_ += readCount_;
      readCount_ = std::fread(buffer_, 1, bufferSize_, fp_);
      bufferLast_ = buffer_ + readCount_ - 1;
      current_ = buffer_;

      if (readCount_ < bufferSize_) {
        buffer_[readCount_] = '\0';
        ++bufferLast_;
        eof_ = true;
      }
    }
  }

  std::FILE *fp_;
  Ch *buffer_;
  size_t bufferSize_;
  Ch *bufferLast_;
  Ch *current_;
  size_t readCount_;
  size_t count_;  //!< Number of characters read
  bool eof_;
};

RAPIDJSON_NAMESPACE_END

#ifdef __clang__
RAPIDJSON_DIAG_POP
#endif

#endif  // RAPIDJSON_FILESTREAM_H_
